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1 vote
Write the sum using summation notation, assuming the suggested pattern continues. -9 - 3 + 3 + 9 + ... + 81

User Mukus
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2 Answers

4 votes
-9 -3 +3 +9 +15 +....+81=15+21+...+81=(23*66)/2=759
User Dave Long
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7 votes

Honestly I believe this is correct:

∑ 15 at the top, n =0 (-9+6n)

User Ali Motameni
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